Method and apparatus for digesting fibrous material



Jan. 15, 1929.

T. L. 'DUNBAR ET AL METHOD AND APPARATUS FOR DIGESTING FIBROUS MATERIAL 4 Sheets-Sheet 1 INVENTOR. f-A ww mq Q. J. W M ATTfiRNEY.

Jan. 15, 1929.

T. L. DUNBAR ETAL METHOD AND APPARATUS For: DIGESTING FIBROUS MATERIAL 4 Sheets-Sheet 2 Filed Dec. 12, 1927 mm w? 1? 4 n wmu Luv WMMXN Jan. 15, 1929.

r. L. DUNBAR ET AL METHOD AND APPARATUS FOR DIGESTING FIBROUS MATERIAL Filed Dec. 12 1927 4 Sheets-Sheet 3 INVEN TOR.

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Jan. 15, 1929.

'r. L. DUNBAR ETAL METHOD AND APPARATUS FOR DIGESTING FIBROUS MATERIAL lkcumulalor High Press re ill Patented Jan.15, 1929.

UNITED STATES PATENT OFFICE.

THOMAS 1.. DUNBAR AND AUGUST 1'. RICHTER, or waranrown, NEW YORK, AS- SIGNORS r CHEMIPULP rnooass INCL, or WATERTOWN, new roan.

Application filed December 12, 1927. Serial No. 239,488.

This invention relates to improvements. in

the processes and apparatus for digesting fibrous material, such as wood chips and the like.

The primary object of the invention is to improve the systems heretofore known 1n such manner that the heat units contained in the exhaust gases, may be more effectively utilize-d, and the gases themselves may be absorbed and thus saved.

Another object ofthe invention is to provide a rocess in which the high pressure gases released. from the digesters may be introduced into an accumulator tank, and in which the low pressure gases may be introduced either into said accumulator or into a siphonic system, through which fresh liquor from a source of supply is circulating.

Another object is to furnish a system in which gas from the accumulator may be vented under its own pressure into one or more of the digesters when the pressure in the latter is below that ofthe accumulator.

A still further object is to provide a system in which the gas from the accumulator may be forced by a pump or the like, into one or more of the digesters, for the purpose of creating a pressure in the digesters .to expedite penetration of the material undergoing treatment, and also for the recovery of the heat units and the S O contained in the gas.

A further' object is to furnish an apparatus including a gas mixer siphon arranged at an elevation above the acid supply and communicating with the latter by means of an unobstructed drop leg pipe extending to the bottom portion'of'theacid supply tank; said siphon being connected by a conduit to the acid tank, and a pump being arranged in this conduit for forcing acid liquor from the supply tank to the drop leg pipe. A passageway connects the siphon with the digester, so that liquor flowing through the siphon will, when the pressure in the digester has fallen sufiiciently, create a suction which will be imparted to the digester for withdrawing gas from the latter.

lVith the foregoing objects outlined and with-other objects in view which will appear as the description proceeds, the invention consists in the novel features hereinafter describedin detail, illustrated in the accompanymg drawings, and more particularly polnted out in the appended clalms.

Referring to the drawings,

Fig. 1 is a plan view of the improved apparatus with which the new process is carried out, certain parts of the apparatus be ing omi ted to facilitate illustration.

Fig. is a vertical sectional view taken on 'line 22 of Fig. 1.

. branch 3; all of these branches being conoutlet I nected to a common high pressure pipe 4.

Low pressure branch pipes 5 are also con nected to the tops of the digesters, and these pipes are connected to a common low pres sure line 6. Suitable valves 7 are arranged in the branch pipes to control the passage of 7 release gases from the digesters into the pipes 4 and 6.

Each digester also has a side relief branch 8 which is connected to the digester at a point some distance below the top of the same, and these branch ipes are connected to a side relief line 9. X valve 10 is provided for each of the side relief branches. f

The pipes 4, 6 and 9 are connected by valved conduits 11, 12 and 13, to a manifold pipe 14, which is connected by a pipe 15 to the lower part of a pressure accumulator tank or chamber 16.

Pipes 11, 12 and 13 are also connected by valved pipes 17, 18 and 19 to aconduit 2O The.

lower end of this drop leg is sealed by' the liquor in the tank.

A later, where through the conduit 27, siphon 21 and drop leg 22. Consequently, a suction will be created in the pipe 20, and this suction may be utilized to draw gas, vapor or liquid from the digesters through the pipes4, 6 and 9.

The pipe 25 is also connected at point 26 to a conduit 28 connected to the upper portion of the accumulator. 16. When suitable valves in the pipes are properly manipulated, the pump 24 may be used to force liquor from the tank 23, either to the siphon or to the accumulator.

The lower portion of the accumulator is connected by a pipe 29 to branches 30 leading to the lower ends of the digesters, and a pump 31 is arranged in the line 29 to force heated liquor from the accumulator into one or more of the digesters.

As is usual in such systems, a steam line 32 is used to supply steam to the digesters, but in the present invention, this line is connected by'valved branch pipes 33 to injectors 34, throu h which the steam passes on its way into the igesters.

We may utilize the force of this steamto cause the injectors to exert suction in valved branch pipes 35, which are connected by a line 36, and pipe 37 to the top of the accumuy gas may be withdrawn from the accumulator by means of the steam injection, and may thus be introduced into the digesters for recovering. the heat units of the gas, and for utilizing the S0 within the digesters, and creating a balanced pressure on the accumulator.

We also connect the pipe 37 by means of "valved branches 38 to the sides of the digesters, so that gas from the accumulator may be fed directly into one or more of the digesters, either under the pressure existing in the accumulator when conditions so permit, or under super-imposed pressure such as can be created by a pump 39 which is connected to the pipe 37 by valved by-pass pipes 40 and 41.

If preferred, the passage of the gas from the accumulator to the digesters may be controlled automatically. For example, the pipe 37 may be provided with a pressure operated valve 42 which will be actuated by pressure existing in the accumulator. When this valve operates, it will, through linkage 43 and 44, operate the valve 45 in the line 36, so that the gases from the accumulator may be automatically fed to the branch pipes 35 leading to the steam injectors.

In the operation of this system, one or more of the digesters is or are charged with chips, and the digester or digesters filled with are opened, and this permits the gases and vapors released, to flow through the pipe 4, preferably into the accumulator by way of pipe 15. At this time, the accumulator is partially filled with acid liquor, and the hot gases from the digesters heats the liquor in the accumulator, and the S0 in the gas 1s absorbed by the liquor.

During the cooking, the pressure in the ac cumulator will increase, and in order to relieve'the same, the gas and vapor, from the accumulator may be vented through pipe 37. From this pipe, it may be fed through the injectors 34 directly back into the digesters from which it originated, or into one of the other digesters.

On the other hand, where conditions will so permit, this gas may be fed through one or more of the, branches 38, directly into the sides of the digesters. If the pressure in the accumulator is insuficient to force the gas through the branches 38, the pressure may be increased by passing the gas through the pump 39.

Our system also includes a valved conduit 50 which connects the upper portion of the accumulator to the siphon 21, so that gases from the accumulator may be directly mixed with liquor passing through the siphon for the purpose of pre-conditioning the acid liquor and absorbing the gas.

After the cooking has advanced in the digester to a certain point, the side relief branch 8 may be opened to permit the excess liquor in the digester to discharge from the same. This liquor will pass into the line 9, and from this line, through suitable pipesto the manifold 14. From the latter, it may flow through the pipe 15, directly to the accumulator, or if so desired, it may be passed by way of pipes 11 and 19, to the pipe 20,

Which willlead the same to the siphon 21, in which it may be mixed with theliquor flowing to the siphon for the purpose of preconditionin the liquor and utilizing the heat units and 0 contained in the side relief branch liquid.

By means of our system, we can utilize the pressure existing in a digester for automatically feeding gases, vapor and liquid from the digester into the accumulator for pre-condi tioning and heating liquor in the accumulator, and as soon as the pressure in the digester has reached a point where it is equal to the pressure existing in the accumulator, the gases may then be withdrawn from the digester by suction from the siphon 21. For example, at the time the low pressure gas and vapor is released, it may flow through the branches and pipe 6, into the pipes 13 and digester, previous to steaming of the latter,

the gas willexert pressure on the acid liquor for causing the liquor to more thoroughly penetrate the material undergoing treatment, which has a distinctadvantage in hastening the delignification of the fibrous material, thereby creating a superior product.

' x By our method we can carry any desired pressure in the accumulator tank, before continuously or intermittently relieving from same. Our usual method of operationis to till set our regulating pressure valve on the accumulator at 35lbs. when'we have a working pressure on the digesters of 60 to 65 lbs.

However, if we carry a workin pressure on the digesters of from to l s., which we do for certain grades of pulp,,we set our pressure regulating valve or accumulator to release at from 4:0 to 45 lbs. pressure. And

under such circumstances, the temperature under normal operating conditions, may go up to 230 Fahrenheit, and on special tests, it ran up to 260.

1F rom the foregoing, it is believed that the construction, and operation of the apparatus, and the working the process may be clearly understood, and we are aware that changes maybe made in the details disclosedwithout departing from the spirit of the invention as expressed in the claims.

What we claim and desire to secure by Letters Patent is:

1. In the treatment of fibrous material, digesting said materialwith acid liquor utilizing the high pressure existing in the digester during a portion of the cooking period for discharging heated high pressure' gas and vapor from the digester during that portion of the cooking period and for introducing the same in its heated condition into acid liquor in, an accumulator, exerting, suctionv on the digester during another portion of the cooking process to withdraw heated low pressure gases and vapors from the digester, contacting these low pressure gases and vapors while in their heated condition with a flowing stream of acid liquor, and utilizing acid liquor thus preconditioned, from the accumulator and flowing stream, for digesting fibrous material.

2. In the treatment of fibrous material,

cooking such material with acid liquor, re

leasing high pressure gas from the digester and introducing the same under its own pres- '-the digesting period, and introducing said sure into acid liquor in an accumulator, releasing low pressure gas from the digester,' mixing the low pressure gas with a flowing stream of acid liquor, and subsequently feeding the last mentioned acid liquor into the accumulator.

3. In the treatment of fibrous material, digesting said material with acid liquor under heat and pressure, releasing high pressure gas and vapor from the digester, and introducing the same in heated condition into acid liquor in an accumulator for heating the liquor and absorbing the gas, releasing 10W pressure gas and va or from the digester and mixing the same-in heated condition with a flowing stream of acid liquor, subsequently feeding the last mentioned acid liquor into the accumulator and utilizing said acid liqnor from the accumulator in its heated condition for digesting fibrous material.

4. In the treatment of fibrous material, digesting the material with acid liquor under heat and pressure, releasing high pressure gas and vapor under their own pressure from the sphere of digestion during aportion of the digesting period, and introducing this high pressure gas and vapor in heated condi-' tion into acid liquor, exerting suction during another portion of the digesting period for withdrawing low pressure gas and vapor 95 from the sphere of digestion, introducing said low pressure gas in heated condition into acid liquor, and utilizing acid liquor thus preconditioned for. rial. m

5. In the treatment of fibrous material, with acidliquor under heat and pressure, releasing high pressuregas and vapor from the sphere, of digestion during a portion of digesting fibrous mategas and vapor in heated condition and under their own pressureinto acid liquor, exerting suction during another portion of the digesting period for withdrawing low pressure gas and vapors from the sphere of digestion, in:

troducing said low pressure gas and vapor ip heated condition into acid liquor, and utilizing said acid liquor thus heated for digesting fibrous material.

6. In the treatment of fibrous material,digesting said material with acid liquor under heat and pressure, releasing high pressure gas and vapor fromthe sphereof digestion during a portion of thedigesting period, and introducing said gas and vapor in heated condition and under their own pressure into a batch of chemical liquor arranged in an accumulator chamber, exerting suction during another portion of the digest-ing period for withdrawing low pressure gas and vapor from the sphere ofdigestion, mixing said low pressure gas and vapor in their heated condition with aflowing stream of acid liq-' uor, and then feeding said stream of acid liquor into said accumulator chamber.

r n 7. A process for recovering the heat units in the exhaust gas and va' or. from a digester,

Ill

lid

andfor reclaiming the S 2 contained in said gas and Vapor, consisting in releasing high pressure gas and vapor froma digester during a portion of the digesting period, and introducing the same under their own pressure and in heated condition, into acid liquor, exerting suction on thedigester during another portion of the digesting period, and thus withdrawing low pressure gas and vapor from the digester, introducing said low pressure gas and vapor in their heated condition, into acid liquor, and utilizing the acid liquor thus heated for cooking fibrous material.

8. In the treatment of fibrous material,

utilizing hot gas and vapor from a digester liquor in an accumulator and also in a pipe line, feeding the acid liquor from the pipe line into said accumulator, and releasing gas and vapor from the top of the accumulator and introducing the same into a digester, at

v a point above the bottom of the latter.

10. In the treatment of fibrous material, releasing gas and vapor from a digester and introducin the same into a batch of acid liquor for eating the latter, and absorbing the S0 from the gas and vapor, releasing gas from said batch of liquor, mixing said gas with steam, and introducing the same into a digester; I v

11. In the treatment of fibrous material, digesting the material with acid liquor, releasing gas and vapor from the digester and introducing the same into a pool of acid liquor in an accumulator, introducing steam into a digester, and utilizing the force of the steam to withdraw gas and vapor. from the accumulator, and to feed the same into a digester.

12. In the treatment of .fibrous material,

withdrawing gas and vapor from a digester and introducing the same into acid liquor contained in an accumulator, withdrawing gasand vapor from the accumulator, superimposing pressure on the gas and vapor from the accumulator and utilizing this superimposed pressure to force said gas into a digester While the latter is undergoing cooking.

13. In the treatment of fibrous material, circulating a stream of acid liquor in an endless path causing said liquor in a part of said endless path to flow by gravity through an unobstructed drop leg passageway, utilizing force created by the'circulation of the liquid for withdrawing low pressure gas and vapor from a. digester during cooking of the latter, mixing this gas and vapor with the circulating liquid to heat the liquor and absorb the gas, also releasing high pressure gas and vapor from the digester under the pressure existing in the latter during a part ofthe cooking period, feeding said high pressure gas and vapor in heated condition into acid liquor inan accumulator, also feeding preconditioned acid liquor from said stream into the accumulator, and utilizing heated acid liquor from the accumulator for digesting fibrous material.

It. In an apparatus for treating fibrous material, a digester, an accumulator, means for introducing acid liquor into the accumu- "lator, means for leading gas and vapor from the digester into the accumulator, means for circulating acid liquor in an endless stream, and means for feeding gas and vapor from the digester into the last mentioned means for heating-the flowing stream of liquid.

15. In an apparatus for treating fibrous material, a digester, an accumulator tank, means for introducing acid liquor into said tank, a conduit for feeding gas and vapor from the digester to the accumulator, means for moving a stream of acid liquor in an end less path, said last mentioned means includan injector, and a passageway placing the ln ector in communication with the digester for feeding gas and vapor from the digester to the injector. v

16. An apparatus for treating fibrous material, comprising a digester, an accumulator, a gas and vapor conducting pipe connecting the digester and accumulator, a conduit for discharging gas and vapor from the digester, a siphon connected to said conduit, means for feeding acid liquor QtO said siphon, and anunobstructedhollow drop leg connected to the siphon.

17. In an apparatus of the character described, an accumulator tank, a digester, and a pipe connecting the upper portion of the accumulator to the digester above the bottom of the latter for introducing gas from the accumulator into the digester.

18. In an apparatus of the character described, a digester, means for introducing steam into said digester, an injector forming part of said means and actuated by the steam, an accumulator ,to contain heated acid liquor, and a-conduit connecting the upper end of the accumulator to said injector for utilizing the force of the steam to withdraw gas from the accumulator. v

19. In an apparatus of the character de scribed, a digester, an accumulator, a conduit for feeding gas from the'accumulator into thedigester, above the bottom of the latter, and a pump interposed in said conduit.

20. An apparatus of the, character det9 the accumulator means, or to the means for circulating the liquor, a pipe for releasing gas and vapor from the accumulator, and a 10 passageway placingkaid pipe in communication with the digester.

THOMAS L. DUNBAR. AUGUST F. RICHTER. 

